There are many products, such as paper towels, napkins and tissues, which are sold in the form of single-folded sheets having a first and second panel A, B joined along a common edge of the panels at a fold line C, in the manner illustrated in FIG. 1. As further illustrated in FIG. 1, such single-folded sheets are often provided in an interfolded stack of sheets, with the first panel of each sheet overlapping the second panel of a successive sheet. By virtue of this arrangement, the interfolded stack of sheets can be dispensed from a dispenser having a sheet stack receptacle width equal to the full width of the first and second panels A, B, with the dispenser further having an opening at one end thereof through which the individual sheets may be dispensed, one-at-a-time, by pulling on an exposed panel extending out of the opening. As each sheet is pulled out of the dispenser, by grasping the first panel A and pulling, the interfolding of the second panel of the first sheet with the first panel of the second sheet causes the first panel of the second sheet to be pulled through the opening in the dispenser and left exposed for use in pulling the next sheet from the dispenser.
Such interfolded stacks of single-folded sheets are often formed with an interfolding apparatus having a pair of count-rotating folding rolls mounted to form a nip between the rolls through which partly-overlapped sheets cut from two separate webs of material are fed to form the interfolded stack. The rolls of such folding machines typically include a plurality of grippers and coordinating tuckers alternately circumferentially spaced at a circumferential difference from one another which is substantially equal to the full panel width of the interfolded sheets. The rolls are operatively connected to counter-rotate in a timed relationship to one another such that the grippers from each roll interact with respective tuckers from the other roll as the coordinating grippers and tuckers pass through the nip. Such an apparatus, and a method for operating such an apparatus, are described in U.S. Pat. No. 5,147,273 to Rottman.
It will be noted that, in a stack of interfolded sheets such as the one illustrated in FIG. 1, the leading and trailing edges of an immediately following and immediately preceding sheet are folded into a given sheet substantially at the fold line of the given sheet. Accordingly, one could refer to the positioning of the leading and trailing edges of the sheets as being “on-fold.”
Machines of this type, and prior methods for their use, have proved to work very well for high-speed production of interfolded stacks of sheets having two identical full width panels joined along a common fold line. During operation of such machines, each sheet is typically grasped by the grippers at both a leading and a trailing edge of the sheet and at the fold line, as the overlapped sheets make their way along a portion of the peripheries of the folding rolls and pass through the nip.
Although single-folded sheets of product having two full-width panels have been widely accepted for many uses through the years, there is now a desire in the marketplace for stacks of interfolded single-folded sheets having one full-width panel E joined along the fold line F to a partial-width panel D in the manner shown in FIG. 2. Because the leading edge of the partial-width leading panel D is not positioned at the fold line F, in a stack of interfolded sheets of the type shown in FIG. 2, such a stack of sheets may be referred to as being “off-fold,” or “off-folded.”
Having one panel be shorter also conserves valuable natural resources, and reduces the cost per sheet, while still allowing the use of existing dispensers configured to dispense single-folded products having two full-width panels.
It is desirable to produce such stacks of interfolded sheets having one full-width and one partial-width panel utilizing interfolding machinery and methods similar to those having proven to be so successful at high-speed production of interfolded stacks of single-folded sheets having two full-width panels, such as those described above and in the U.S. Pat. No. 5,147,273 patent to Rottman cited above. It would also be highly desirable to be able to manufacture either the traditional interfolded stacks of single-folded sheets having two full-width panels, and, alternatively, inter-folded stacks of single-fold sheets having one full-width and one partial-width panel on the same interfolding machine.
In order to make interfolded stacks of single-fold sheets having one full-width and one partial-width panel on a conventional interfolding machine having grippers and tuckers spaced at circumferential distances equal to a full-panel width, a substantial problem must be overcome. When the sheets having one partial-width panel are run through the machine, the grippers and tuckers cannot be used to grasp one end or the other of the sheet. Providing a method and apparatus for controlling the end of the sheet adjacent the partial panel presents a considerable technical challenge. The end of the partial-width panel falling between adjacent tuckers and grippers cannot be allowed to hang free as the sheet interacts with the folding roll during high-speed operation. An uncontrolled free-hanging edge would lead to mis-folded product, and other problems such as jamming of the interfolder or damage to the interfolder, thus precluding operation at the high production speeds necessary to keep the interfolded products at a low enough cost to compete in the marketplace.
A need exists in the industry, therefore, to provide a method and apparatus for producing off-folded towel or tissue products, and the like, in a single-fold interfolding machine having grippers and tuckers circumferentially spaced around the folding rolls at a full-panel circumferential distance. It is also highly desirable to provide such a method and apparatus in a form which will allow production of both traditional single-folded sheets having two identical panels, and off-folded products having a full-width panel and a partial-width panel in a single interfolding machine.